Improvement in wood-screws



G. 0. ARMSTRONG.

Wood-Screw. v

No. 2o5,99o.- I Pa tented July 16, 1878.

WiTn EEEE. Q \hvnmr.

N. PETERS. FHOTO-LITHOGRAPHER, WASHlNGTDN -of Brooklyn, Kings county, New York, have specification:

U I ED STAT-Es PATENT Orr-non.

GEORGE o. ARMSTRONG, OFIBROOKLYN, NEW YORK.

IMPROVEMENT IN WOOD-SCREWS.

Specification forming part o f Lctters Patent No. 206,990, dated July 16, 1878 application filed April 13, 1 878.

into hard wood, if the countersink has not been drilled deep enough, the screw must be removed and the drill used again, as the head must be forced to its seat by the threads on. the body of the screw, and when the head Teaches the surface of the wood there is a ten den'cy for the'head to break off. This is very To all whom it may concern.

Be it known that I, GEORGE O. ARMSTRONG,

invented certain new and useful Improvements in Wood-Screws, of which the following is a The object of my invention is to provide an improved wood-screw that will hold more firmly, require less countersinking than ordinary screws, and prevent the screw-driver slipping from the slot.

My invention may be stated to consist in an. improved screw having the under side of its another substituted, which in fine work is very troublesome.

This tendency of the head to break is almost entirely obviated in my improved screw, for the head is not pulled into its seat bodily,

and its slot corrugated, as hereinafter set forth.

In the annexed drawing, Figure 1 is a plan view of my improved 'screw,'an d Fig. 2 is an elevation thereof.

A represents the body of the screw, which is threaded in the usual manner. B isthe conical or countersunk head, which, accordin g to my invention, is threaded on its under or conical side, as shown, the thread being preferably finer, but of the same pitch as that on the body of the screi The extreme upper edge of the head is beveled, as shown at O. 1) represents the slot of the head, which is cut centrally and transversely, as usual; but the vertical sides thereof are made slightly beveling, as represented, and these sides are corrugated with fine dentations or corrugations, as shown.

ened upon soft wood, for the hold of the threads in the soft wood is often not strong enough to draw the head of the screw into the countersoft wood often break and loose their hold.

In my improved screw the threaded head obviates this difficulty, and enables the two kind s of wood to be held firmly together.

In removing screws that have been screwed below the surface, the edge of the screw-head sometimes catches in the wood and breaks the head or tears or cuts the sides of the countersink.

]n my improved screw the upper edge of the head is beveled, as shown at O, and this enables the head to thus relieve itself without tearing the wood.

The corrugated slot of the head prevents the screw-driver from slipping and dentin g ishingroundheaded screws, theheads of which are usually formed of ornamental plated caps,

which are easily torn or injured by the slipping of the screw-driver from the slot.

In my improved screw little or no countersinking will be necessary, except in the hardest be either single or double, and of a pitch corklnds of wood, and then only to a trifling exresponding to the body-threads A, or a little finer, as may be found most suitable in screws of different kinds arid sizes.

I am aware that screws have been made the annoying, as the screw must be remox'ed and slnk 1n the hard wood, but the threads in the The thread B on the head of the screw may head-slots of which have been corrugated on 2. A screw the head-slot of which is dented their bottom side, but not on their vertical or corrugated upon its vertical sides, substansides, as in my invention. tially as and for the purpose set forth.

What I claim as my invention is- 1. As a new article of manufacture, a wood- GEORGE G. ARMSTRONG.

screw having its head provided on the under side with a screw-thread of apiteh concordant Witnesses:

with the thread on the body of the screw, sub- CHAS. M. HIGGINS, itantialiy as and for the purpose herein set EDWARD H. WALES. orth. 

